152 LECTURES 



anthracite. These two substances are doubtless similar in their 

 origin as well as in chemical composition, the great difference in their 

 density being due only to the pressure under which the change took 

 place. Anthracite is produced slowly under enormous pressure, while 

 coke is produced under ordinary atmospheric pressure, and the rapid 

 disengagement of gas renders it light and porous. 



THE PLANTS OF THE COAL — THEIR STRUCTURE AND AFFINITIES. 



Geology is the latest developed among the sciences. This is not an 

 accidental phenomenon in the history of human intellectual progress, 

 but one absolutely necessary, and the cause of which we can clearly 

 trace. The great divisions of science in the order of their complexity 

 are mathematics, mechanical sciences, chemical sciences, organical 

 sciences, and geology. The first is limited to ideas of number and 

 quantity ; the second comprises, in addition to the preceding, ideas of 

 force ; the third, in addition, ideas of chemical affinity ; the fourth, in 

 addition to the preceding, ideas of life, and the last, in addition to 

 all the preceding, ideas of historic development. Now, this order of 

 increasing complexity has necessitated a corresponding order of devel- 

 opment in time. It is impossible that mechanics and physics should 

 have assumed even the form of a science until mathematics was 

 already mature. And so of the rest. Together they form a column, 

 of which mathematics is the pediment and geology the capital ; or, 

 rather, I should say, a magnificent temple, of which mathematics 

 forms the solid foundation and geology the heaven pointing spire ; the 

 most wonderful and perfect work which human genius has erected in 

 honor of Deity. 



It is evident, therefore, that geology was compelled to await the 

 development of other sciences. She could not come forward until her 

 time was fulfilled, for her problems are the most complex and difficult 

 which are to be found in the whole range of science. It is evident, 

 also, that the geologist must be thoroughly accomplished in all de- 

 partments of science. He must be thoroughly grounded in mechanical 

 and physical sciences, or how shall he reason successfully on the up- 

 heaval of continents, the formation of mountain chains, the dynamics 

 of earthquakes and volcanoes, the actions of currents, &c. He must 

 be familiar with chemistry, for disintegration and consolidation of 

 rocks, the deposits of springs, the formation of coal^ are chemical 

 quebtions. Still more necessary to him is an acquaintance with organic 

 science, for the organic remains are the Divine hieroglyphs in which 

 the history of the earth is recorded. It is this very complexity^ this 

 very elevation in the scale, this almost universal culture required of 

 her votaries, which constitutes the greatest obstacle in the way of real 

 progress in this science. I know it is thought by many that geology 

 is an easy and simple science, that any one, by industrious collection 

 of fossils and persevering exercise of memory^ may be a good geolo- 

 gist ; but this is a sad and very pernicious error. In so vast a science 

 collectors of materials must be numerous, but the philosophical gen- 

 eralizer is very rare. In so vast an edifice the fetchers of stone and 

 brick and mortar are innumerable, but heaps of brick and stone and 



